Power-generating machines, such as internal combustion engines, motors, and generators, typically include rotary assemblies featuring rotating shafts. Sensors may be used to monitor and measure certain properties of a rotating shaft within a power-generating machine to evaluate performance and/or health of the power-generating machine. For example, monitoring properties such as torque, temperature, rotating speed, and strain of the shaft may enable early detection of sub-optimal machine performance and/or components needing maintenance.
Monitoring one or more properties of the rotating shaft of a rotary assembly typically requires one or more discrete sensors installed on or proximate to the shaft. The signals generated by the one or more sensors may be remotely communicated to a processing unit, such as a controller, that is spaced apart from the shaft for analysis of the signals to determine the measured properties. The signals generated by the one or more sensors are susceptible to electromagnetic interference during the communication of the signals to the processing unit, which degrades the signal-to-noise ratio. Interference outside of the operating frequency range of the sensor system (e.g., outside of the sensor signal frequencies) can be filtered using traditional filter technology in the signal transmission pathway, but interference at frequency bands within the operating frequency range of the sensor system cannot be filtered because the sensor signals would be filtered as well. The interference may mask the sensor signals, reducing the likelihood that the processing unit is able to correctly interpret the signals. As a result, the sensor system may have diminished accuracy or, in some cases, may be completely inoperable.
To block electromagnetic interference, electrically conductive shielding may be utilized to surround portions of the sensor systems. However, it is difficult to provide adequate shielding around a sensor disposed on a rotating shaft because electromagnetic surface currents can be conducted along the length of the shaft. Shielding that physically contacts the surface of the shaft to block such surface currents may introduce additional costs and challenges, such as increased wear on the shaft due to the rubbing of the shielding, the need for more frequent maintenance, excessive heat generated by the rubbing, and/or the like. A need remains for a sensor system that can be incorporated with a rotating shaft of a rotor assembly to accurately determine one or more properties of the shaft by limiting or resisting electromagnetic interference on the sensor system.